1. Technical Field of the Invention
The present invention relates to a three dimensional information measurement method and apparatus for measuring three dimensional information on an object over a wide angular range, and for inputting the measured information, and more particularly to a three dimensional information measurement method and apparatus capable of making measurements over an angular range, for example, of 180 or 270 degrees, or from all directions through 360 degrees.
2. Description of Related Art
Recent years have seen rapid advances in virtual reality and mobile robot technologies. In these fields, it is required to input three dimensional information of objects that are to be captured for imaging or detection, and with this requirement, interest in and demand for three dimensional information measurement apparatuses have been increasing.
In the case of a mobile robot, when the robot moves, it is necessary to constantly monitor the surroundings for obstructions in order to avoid collisions, and to steer away from any obstructions. Whether an object located in the surrounding space is an obstruction or not is judged by measuring the distance to the object by a three dimensional information measurement apparatus mounted on the mobile robot, and by checking if the distance has decreased below a predetermined value. Such judgement must be made in real time, requiring that the distance in each direction be measured at high speed around the entire circumference.
In a known technique for measuring the distances to surrounding objects over a wide angular range, it has been practiced to rotate the camera part of the distance measurement apparatus while shooting the surroundings. If the rotational speed is slow, the time difference between the timing of the camera's line of sight capturing an object in one direction and the timing of capturing an object in the next direction increases, resulting in slow monitoring. If the rotational speed is increased, the camera's line of sight quickly scans the surroundings, so that the time difference is reduced and quick monitoring can be achieved. This, however, increases the size of the mechanism provided for that purpose, and also, rotational noise becomes a problem.
There has been proposed an omnidirectional distance detection apparatus in which, instead of rotating the camera part, two mirrors for projecting and receiving reference light for distance measuring are assembled in one unit and are rotated together (Japanese Patent Unexamined Publication No. 7-191142). However, in the omnidirectional distance detection apparatus disclosed in the above patent publication, the mirrors are housed in a cylindrically shaped casing having a transparent circumferential wall and are rotated about the axis of the casing to irradiate surrounding objects with reference light and to receive its reflected light for distance measuring. The mirrors are driven by a motor via a rotor, and the rotor, motor, etc. are all housed in the casing, providing the effect of reducing the rotational noise. The construction is complex compared with the method of rotating the camera's line of sight. Since the two mirrors for projecting and receiving the reference light are rotated together, the apparatus size increases, and the stability of the apparatus decreases when the rotational speed is increased.